Difference Families, Skew Hadamard Matrices, and Critical Groups of Doubly Regular Tournaments
Difference Families, Skew Hadamard Matrices, and Critical Groups of Doubly Regular Tournaments
In this paper we investigate the structure of the critical groups of doubly-regular tournaments (DRTs) associated with skew Hadamard difference families (SDFs) with one, two, or four blocks. Brown and Ried found that the existence of a skew Hadamard matrix of order $n+1$ is equivalent to the existence of a …